Polymer and Photonic Materials Towards Biomedical Breakthroughs

Polymeric materials that respond to light stimulus represent an important research area in the field of biomaterials. Light-responsive biomaterials have received significant attention due to their ability to provide spatially and temporally control and their potential to be less invasive. In this book chapter, we highlight the exciting progress realized in the biomedical field in recent years on photoresponsive polymeric systems. More precisely, we discuss the rational design of photoactive compounds, the role they have in the photoresponsive systems, the underlying principles behind photoresponsive behavior, and the subsequent applications in the biomaterial field. We also present the progress made in the field of photopharmacology, photoregulated drug delivery, and bioimaging, emphasizing the advantages on the basis of different architectures such as micelles, hydrogels, nanoparticles, and photoresponsive supramolecular assemblies. Finally, analytical techniques used to characterize the photoresponsive materials are expound.

Since 3D printing became widely available for a variety of applications, the demand for three-dimensional structures with high resolution has grown. Direct laser writing by multiphoton polymerization, due to its unique, nm-scale resolution, has proven to be an indispensable tool for high-accuracy 3D printing. Here, we will discuss the basic principles of direct laser writing by multiphoton polymerization, the equipment used, and the most commonly employed materials. Finally, we will discuss its application in the field of tissue engineering.

In tissue engineering, three-dimensional scaffolds, which should ensure necessary mechanical and biological microenvironment and nutrient, oxygen and grow factor delivery to proliferating cells, are an essential element. They can be formed from polymeric, ceramic and hybrid materials via different techniques. Modern laser fabrication methods, which provide high accuracy of positioning and energy focusing and allow the precise porous scaffold formation, are particularly interesting. Two-photon polymerization is one of the most promising laser-based techniques and permits the use of a large material variety for scaffold fabrication with the possibility of controlling accurately their microarchitecture. While the number of studies on two-photon polymerization is constantly growing, it is crucial to provide a framework of its application in tissue engineering. Therefore, this chapter aims to describe recent achievements and examples of two-photon polymerization application in tissue engineering and to reveal the main trends in this field.

In biomechanical and mechanobiological applications, the ability of photo-activatable materials to change properties in response to a light (photo) stimulus offers key potential advantages over other activatable materials. Not only can photo-activatable materials be used in close contact or proximity to cells and tissues without the cells or tissues being affected by the photostimulus, but photo-activatable materials also offer a level of spatiotemporal control unavailable with many other forms of smart material triggering, such as ambient heating or hydration. This chapter will give an overview of photo-activatable materials that have been developed to study cell biomechanics and mechanobiology and discuss future potential applications for these promising materials.

This chapter is focused on the application of photonics in medicine, namely, in the systems designed to facilitate delivery of bioactive agents (drugs, photosensitizers). The introduction of the carrier into such systems allows to increase their efficiency, to reduce side-effects and to precisely control the dose, the place and time of delivery inside the patient’s body. Three main aspects of the problem are analysed in this chapter: (1) using light-sensitive probes to study pharmacokinetics of drugs; (2) the choice of the application route for the photosensitizers used in photodynamic therapy (PDT), including prodrugs, micelles, inorganic and hybrid nanoparticles and virus capsids; and (3) achieving targeted delivery and precise control over the release profiles by the application of the systems containing photoresponsive carriers. The basic mechanisms of the photophysical and photochemical processes involved are discussed, including PDT, photoinduced NO delivery and light-triggered release of drugs from liposomes, prodrugs and other specific systems. The most interesting examples are described, and the advantages and limitations of using various systems are discussed.

The treatment of diseases at genetic level seems a virtual certainty due to revolutionary advances in cell and molecular biology in the past two decades. Gene therapy has attracted increasing interest as a possible therapy for treating a wide variety of diseases, including both genetic and non-genetic disorders. It is an experimental technique that delivers genetic material to somatic or germ cells of patients, with the intent of altering cellular function or structure at the molecular level to improve a clinical outcome (Anderson, Nature 392, 25–30, 1998). The exogenous genetic material that is introduced into the cells can be either plasmid DNA or one or more specific genes. The latter are often referred to as transgenes. A plasmid, on the other hand, is a DNA molecule which differs from chromosomal DNA and has the ability to replicate independently of it (Sun and Lee, Am. J. Biochem. Biotechnol. 2(2), 66–72, 2006). Several gene therapy approaches have already been evaluated, including the replacement of a mutated gene causing illness with a healthy copy of the gene, the inactivation of an improperly functioning mutated gene, and the introduction of a new gene into the body to help in countering a disease (Abramson et al. Genet. Home Ref. 1(7), 123–131, 2010). Clearly, gene therapy should be applicable in clinical settings and not only in a laboratory. The most important prerequisites include a sufficient DNA delivery and a sustained expression of its secretory products, often proteins. For some purposes, such as the stimulation of vascular growth, short-term activity can suffice, while for others (e.g., the rectification of a genetic defect), long-term gene expression can be required (Strayer, Expert Opin. Investig. Drugs 8(12), 2159–2172, 1999). The current chapter will overview the state-of-the-art covering viral and non-viral gene delivery approaches for a range of biomedical applications.